Unlike the normal Mog event mode, it is better to make use of Elemental Chain and cast it’s elemental weakness spell to do more damage and conserve your MP. Remember to always check which elemental weakness it’s Barrier Change, changed into.

It seems that the first 2 turns will always be Lightning weakness. (TBC)

Not sure if Barrier Shift is bugged but it kept remaining as Lightning Resistance for me (TBC).